<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html><html xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <title>glGetUniformLocation - OpenGL ES 3.1 Reference Pages</title>
    <link rel="stylesheet" type="text/css" href="opengl-man.css"/>
    <meta name="generator" content="DocBook XSL Stylesheets V1.78.1"/>
    <script type="text/x-mathjax-config">
            MathJax.Hub.Config({
                MathML: {
                    extensions: ["content-mathml.js"]
                },
                tex2jax: {
                    inlineMath: [['$','$'], ['\\(','\\)']]
                }
            });
        </script>
    <script type="text/javascript" src="https://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML"/>
  </head>
  <body>
    <header/>
    <div class="refentry" id="glGetUniformLocation">
      <div class="titlepage"/>
      <div class="refnamediv">
        <h2>Name</h2>
        <p>glGetUniformLocation — Returns the location of a uniform variable</p>
      </div>
      <div class="refsynopsisdiv">
        <h2>C Specification</h2>
        <div class="funcsynopsis">
          <table style="border: 0; cellspacing: 0; cellpadding: 0;" class="funcprototype-table">
            <tr>
              <td>
                <code class="funcdef">GLint <strong class="fsfunc">glGetUniformLocation</strong>(</code>
              </td>
              <td>GLuint <var class="pdparam">program</var>, </td>
            </tr>
            <tr>
              <td> </td>
              <td>const GLchar *<var class="pdparam">name</var><code>)</code>;</td>
            </tr>
          </table>
          <div class="funcprototype-spacer"> </div>
        </div>
      </div>
      <div class="refsect1" id="parameters">
        <h2>Parameters</h2>
        <div class="variablelist">
          <dl class="variablelist">
            <dt>
              <span class="term">
                <em class="parameter">
                  <code>program</code>
                </em>
              </span>
            </dt>
            <dd>
              <p>Specifies the program object to be
            queried.</p>
            </dd>
            <dt>
              <span class="term">
                <em class="parameter">
                  <code>name</code>
                </em>
              </span>
            </dt>
            <dd>
              <p>Points to a null terminated string containing
            the name of the uniform variable whose location is
            to be queried.</p>
            </dd>
          </dl>
        </div>
      </div>
      <div class="refsect1" id="description">
        <h2>Description</h2>
        <p><code class="function">glGetUniformLocation </code> returns an
    integer that represents the location of a specific uniform
    variable within a the default uniform block of a program object. 
        <em class="parameter"><code>name</code></em> must be a null terminated string 
        that contains no white space. <em class="parameter"><code>name</code></em> must 
        be an active uniform variable name in <em class="parameter"><code>program</code></em> 
        that is not a structure, an array of structures, or a subcomponent 
        of a vector or a matrix. This function returns -1 if 
        <em class="parameter"><code>name</code></em> does not correspond to an active uniform variable in
    <em class="parameter"><code>program</code></em> or if <em class="parameter"><code>name</code></em>
        is associated with a named uniform block.
        </p>
        <p>Uniform variables that are structures or arrays of
    structures may be queried by calling
    <code class="function">glGetUniformLocation</code> for each field within
    the structure. The array element operator "[]" and the
    structure field operator "." may be used in
    <em class="parameter"><code>name</code></em> in order to select elements within
    an array or fields within a structure. The result of using these
    operators is not allowed to be another structure, an array of
    structures, or a subcomponent of a vector or a matrix. 
        The first element of a uniform array is identified using the name 
        of the uniform array appended with "[0]". If the last part 
        of the string name indicates a uniform array, then the location of the 
        first element of that array can be retrieved by either using the name of
        the array, or by using the name appended by "[0]".</p>
        <p>
        Locations for sequential array indices are not required to be sequential. The
        location for "a[1]" may or may not be equal to the location for 
        "a[0]" + 1. Furthermore, since unused elements at the end of uniform 
        arrays may be trimmed the location of the i + 1 array element may not be valid 
        even if the location of the i element is valid. As a direct consequence, the
        value of the location of "a[0]" + 1 may refer to a different uniform 
        entirely. Applications that wish to set individual array elements should query 
        the locations of each element separately.
        </p>
        <p>The actual locations assigned to uniform variables are not
    known until the program object is linked successfully. After
    linking has occurred, the command
    <code class="function">glGetUniformLocation</code> can be used to obtain
    the location of a uniform variable. This location value can then
    be passed to
    <a class="citerefentry" href="glUniform.xhtml"><span class="citerefentry"><span class="refentrytitle">glUniform</span></span></a>
    to set the value of the uniform variable or to
    <a class="citerefentry" href="glGetUniform.xhtml"><span class="citerefentry"><span class="refentrytitle">glGetUniform</span></span></a>
    in order to query the current value of the uniform variable.
    After a program object has been linked successfully, the index
    values for uniform variables remain fixed until the next link
    command occurs. Uniform variable locations and values can only
    be queried after a link if the link was successful.</p>
      </div>
      <div class="refsect1" id="errors">
        <h2>Errors</h2>
        <p><code class="constant">GL_INVALID_VALUE</code> is generated if
    <em class="parameter"><code>program</code></em> is not a value generated by
    OpenGL.</p>
        <p><code class="constant">GL_INVALID_OPERATION</code> is generated if
    <em class="parameter"><code>program</code></em> is not a program object.</p>
        <p><code class="constant">GL_INVALID_OPERATION</code> is generated if
    <em class="parameter"><code>program</code></em> has not been successfully
    linked.</p>
      </div>
      <div class="refsect1" id="associatedgets">
        <h2>Associated Gets</h2>
        <p><a class="citerefentry" href="glGetActiveUniform.xhtml"><span class="citerefentry"><span class="refentrytitle">glGetActiveUniform</span></span></a>
    with arguments <em class="parameter"><code>program</code></em> and the index of
    an active uniform variable</p>
        <p><a class="citerefentry" href="glGetProgramiv.xhtml"><span class="citerefentry"><span class="refentrytitle">glGetProgramiv</span></span></a>
    with arguments <em class="parameter"><code>program</code></em> and
    <code class="constant">GL_ACTIVE_UNIFORMS</code> or
    <code class="constant">GL_ACTIVE_UNIFORM_MAX_LENGTH</code></p>
        <p><a class="citerefentry" href="glGetUniform.xhtml"><span class="citerefentry"><span class="refentrytitle">glGetUniform</span></span></a>
    with arguments <em class="parameter"><code>program</code></em> and the name of a
    uniform variable</p>
        <p>
          <a class="citerefentry" href="glIsProgram.xhtml">
            <span class="citerefentry">
              <span class="refentrytitle">glIsProgram</span>
            </span>
          </a>
        </p>
      </div>
      <div class="refsect1" id="versions">
        <h2>API Version Support</h2>
        <div class="informaltable">
          <table style="border-collapse: collapse; border-top: 2px solid ; border-bottom: 2px solid ; border-left: 2px solid ; border-right: 2px solid ; ">
            <colgroup>
              <col style="text-align: left; "/>
              <col style="text-align: center; " class="firstvers"/>
              <col style="text-align: center; "/>
              <col style="text-align: center; " class="lastvers"/>
            </colgroup>
            <thead>
              <tr>
                <th style="text-align: left; border-right: 2px solid ; ">
                 
            </th>
                <th style="text-align: center; border-bottom: 2px solid ; " colspan="3">
                <span class="bold"><strong>OpenGL ES API Version</strong></span>
            </th>
              </tr>
              <tr>
                <th style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>Function Name</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>2.0</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>3.0</strong></span>
            </th>
                <th style="text-align: center; border-bottom: 2px solid ; ">
                <span class="bold"><strong>3.1</strong></span>
            </th>
              </tr>
            </thead>
            <tbody>
              <tr>
                <td style="text-align: left; border-right: 2px solid ; ">glGetUniformLocation</td>
                <td style="text-align: center; border-right: 2px solid ; ">✔</td>
                <td style="text-align: center; border-right: 2px solid ; ">✔</td>
                <td style="text-align: center; ">✔</td>
              </tr>
            </tbody>
          </table>
        </div>
      </div>
      <div class="refsect1" id="seealso">
        <h2>See Also</h2>
        <p><a class="citerefentry" href="glLinkProgram.xhtml"><span class="citerefentry"><span class="refentrytitle">glLinkProgram</span></span></a>,
    <a class="citerefentry" href="glUniform.xhtml"><span class="citerefentry"><span class="refentrytitle">glUniform</span></span></a></p>
      </div>
      <div class="refsect1" id="Copyright">
        <h2>Copyright</h2>
        <p>
            Copyright <span class="trademark"/>© 2003-2005 3Dlabs Inc. Ltd.
            Copyright <span class="trademark"/>© 2010-2014 Khronos Group.
            This material may be distributed subject to the terms and conditions set forth in
            the Open Publication License, v 1.0, 8 June 1999.
            <a class="link" href="http://opencontent.org/openpub/" target="_top">http://opencontent.org/openpub/</a>.
        </p>
      </div>
    </div>
    <footer/>
  </body>
</html>
